1. Field of the Invention
The present invention relates to a packaging apparatus and, more specifically, to a packaging apparatus for packaging articles with a weldable and heat-contractive film.
2. Description of the Prior Art
Generally a conventional packagaing apparatus for packaging articles in a weldable and heat-contractive film comprises an article feeding device, a film feeding device, a forming device for folding a weldable and heat-contractive film in a tubular shape, a seling device for welding the seam of a package and separating the package from the film by heat-cutting, and a heat tunnel for making the packaging film heat-contract.
In packaging articles on a conventional packaging apparatus, the film is folded in a tubular shape continuously by folding the opposite side edges downward and then inward, while articles are inserted one by one into an opening formed by the film folded in a tubular shape. In folding the film, the side edges of the film are made to overlap each other to form a seam along one side edge of the package of on the underside of the package. In finishing the package, the seam is welded or the unfinished package is subjected to heat-contraction without welding the seam. Since the sealed package has an undersirable apperarance when the package has a seam along the side edge thereof, it is desirable to form a seam on the underside of the package particularly in packaging an article which attaches importance to the appearance and morphology of the package.
On a packaging apparatus capable of packaging articles in packages each having a seam on the underside thereof, a flat sheet fed to the forming device is formed in a tubular shape by folding the opposite side edges downward and then inward by the forming device, then the opposite side edges are guided inward, namely, toward each other, with right and left guide rollers to form and hold the seam, and then the seam is sealed, when necessary, with a sealing device. In packaging articles on this packaging apparatus, articles are fed to the packaging station sequentially at regular intervals by means of a belt provided with fingers arranged at regular intervals; the package is delivered from the packaging station to a continuously rotating conveyor belt disposed next to the packaging station; and the film is pulled out from the film feeding device by the advancement of the package on the conveyor belt. This manner of feeding the film is achieved by known methods and apparatus, in which the package is held at a fixed position on the moving conveyor belt by its own dead weight, with a pressure belt applied thereto or by vacuum produced by a vacuum mechanism so that the film is fed as the package is conveyed by the conveyor belt.
However, since a packaging apparatus of this type folds the film in a tubular shape by a forming device, inserts an article into an opening formed by folded film, and guides the opposite side edges of the folded film inward to make the opposite side edges overlap each other to form a seam and holds the seam with the right and left guide rollers, which deteriorates the appearance of the package and causes faulty sealing of the package due to the deviation of the seam from the sealing head.
Furthermore, in packaging articles on such a conventional packaging apparatus, since a package containing an article is delivered from the packaging station to the continuously rotating conveyor belt disposed next to the packaging station and the film is pulled out continuously from the film feeding device by the advancement of the package, an imply package is formed when the article feeding conveyor fails to feed the next article to the packaging station, and thereby the corresponding amount of the film is wasted. Further, since the sealing device is actuated at regular intervals, articles need to be fed at regular intervals and it is impossible to package articles satisfactorily when the articles are irregular in size.
Still further, since the film is pulled out from the film feeding device by the advancement of the package held at a fixed position on the conveyor belt by its own dead weight, a light article is unable to pull out the film smoothly. In order to solve such a problems, an apparatus which holds the package on the conveyor belt with a pressure belt have been proposed. However, those apparatus are complicated in construction and expensive.